The present invention relates generally to improvements in microfilm reader apparatus and it relates more particularly to an improved film carrier for microfilm readers, that is a device for a microfilm reader for firmly holding a microfilm sheet sandwiched between a base plate and a cover plate or holder which permits the automatic insertion, withdrawal and replacement of a microfilm sheet in the carrier.
The microfilm carriers heretofore available or proposed in microfilm readers possess numerous drawbacks and disadvantages. In their use in automatic film loading and withdrawing the following problems have been generally encountered.
If the microfilm curls, for one reason or another, particularly if it curls in such a manner that it may protrude from the sides of the film guides, it partly protrudes from the guides or the holder after it is inserted in the carrier device. Then when the carrier apparatus moves in the X-Y direction to select the desired frame, damage may occur to the microfilm itself or to the detecting or selecting mechanism. Besides, since the microfilm is not inserted properly, if the detecting means is operated, the frame may not be accurately selected.
Further, in the microfilm inserting position, the distance between the contact of a pair of feed rollers and a pair of film stops on the base plate of the carrier apparatus is made shorter than the length of the microfilm in the feeding direction. Consequently, the microfilm curls a little when it engages the stops upon its insertion; when the carrier apparatus withdraws from the rollers in this condition, the microfilm may be separated from the stops by reason of its elasticity; and even if the required frame is detected, it may be dislocated from its normal position and a defective image may be projected.
In a carrier apparatus for a microfilm reader which is designed to automatically detect and select a frame, it is difficult to completely eliminate the unsteadiness of the rotary axis of the holder or cover plate in the axial direction. Therefore, difficulty occurs in that the said holder slips during the selecting or detecting action, and the microfilm is accordingly dislocated from its normal position. Moreover, the film guide members on the base plate are usually bonded to the base plate itself. If, however, their bonded condition is imperfect, it may happen that the microfilm is not inserted as required because it will be nipped or wedged between the guide members and the base plate.